Refrigerant compositions

ABSTRACT

A composition comprising 
     (A) 1,1,2,2,3-pentafluoropropane(CF 2 HCF 2 CFH 2 ) and 
     (B) at least one hydrofluorocarbon selected from the group consisting of 1,1,1,3,3-pentafluoropropane (CF 3 CH 2 CF 2 H) and 1,1,1,2,2,3,3,4,4-nonafluorobutane (CF 3 CF 2 CF 2 CF 2 H) is described. The composition is useful as a refrigerant and may be used in chillers as a replacement for refrigerant R-11.

This invention relates to compositions which are suitable forrefrigeration applications and to the use of such compositions in heattransfer devices such as refrigeration and air conditioning systems. Theinvention relates, in particular, to refrigerant compositions which canbe used in the applications currently satisfied bytrichlorofluoromethane (refrigerant R-11).

Heat transfer devices of the mechanical compression type such asrefrigerators, freezers, heat pumps and air conditioning systems arewell known. In such devices a refrigerant liquid of a suitable boilingpoint evaporates at low pressure taking heat from a neighbouring heattransfer fluid. The resulting vapour is then compressed and passes to acondenser where it condenses and gives off heat to another heat transferfluid. The condensate is then returned through an expansion valve to theevaporator so completing the cycle. The mechanical energy required forcompressing the vapour and pumping the liquid may be provided by anelectric motor or an internal combustion engine.

In addition to having a suitable boiling point and a high latent heat ofvaporisation, the properties preferred of a refrigerant include lowtoxicity, non-flammability, non-corrosivity, high stability and freedomfrom objectionable odour.

Hitherto, heat transfer devices have tended to use fully and partiallyhalogenated chlorofluorocarbon refrigerants such asbromotrifluoromethane (refrigerant R-13B1), trichlorofluoromethane(refrigerant R-11), dichlorodifluoromethane (refrigerant R-12),chlorodifluoromethane (refrigerant R-22) and the azeotropic mixture ofchlorodifluoromethane and chloropentafluoroethane (refrigerant R-115);the azeotrope being refrigerant R-502. Refrigerant R-11, for example,has been widely used in chillers.

However, the fully halogenated chlorofluorocarbons in particular havebeen implicated in the destruction of the earth's protective ozone layerand as a result the use and production thereof has been limited byinternational agreement.

Whilst heat transfer devices of the type to which the present inventionrelates are essentially closed systems, loss of refrigerant to theatmosphere can occur due to leakage during operation of the equipment orduring maintenance procedures. It is important, therefore, to replacefully halogenated chlorofluorocarbon refrigerants by materials havinglow or zero ozone depletion potentials.

In addition to the possibility of ozone depletion, it has been suggestedthat significant concentrations of chlorofluorocarbon refrigerants inthe atmosphere might contribute to global warming (the so-calledgreenhouse effect). It is desirable, therefore, to use refrigerantswhich have relatively short atmospheric lifetimes as a result of theirability to react with other atmospheric constituents such as hydroxylradicals.

Replacements for some of the chlorofluorocarbon refrigerants presentlyin use have already been developed. These replacement refrigerants tendto comprise selected hydrofluoroalkanes, i.e. compounds which containonly carbon, hydrogen and fluorine atoms in their structure. Thus,refrigerant R-12 is generally being replaced by1,1,1,2-tetrafluoroethane (R-134a).

Although suitable replacement refrigerants are available, there isalways a need for new refrigerants having a low or zero ozone depletionpotential that are capable of replacing the chlorofluorocarbonrefrigerants presently in use such as R-11. Furthermore, very realbenefits could be realised by a new replacement refrigerant having ahigher refrigeration capacity than the chlorofluorocarbon refrigerant itis replacing.

The present invention provides a composition comprising a mixture ofcompounds having zero ozone depletion potentials which can be used, forexample, in chillers as a replacement for refrigerant R-11. Thecomposition of the invention can exhibit an advantageously highrefrigeration capacity.

According to the present invention there is provided a compositioncomprising:

(A) 1,1,2,2,3-pentafluoropropane (CF₂HCF₂CFH₂); and

(B) at least one hydrofluorocarbon selected from the group consisting of1,1,1,3,3-pentafluoropropane (CF₃CH₂CF₂H) and1,1,1,2,2,3,3,4,4-nonafluorobutane (CF₃CF₂CF₂CF₂H).

The present invention also provides a heat transfer device, such as achiller, comprising an evaporator, a condenser, a compressor and anexpansion valve in which there is contained a refrigerant compositioncomprising:

(A) 1,1,2,2,3-pentafluoropropane (CF₂HCF₂CFH₂); and

(B) at least one hydrofluorocarbon selected from the group consisting of1,1,1,3,3-pentafluoropropane (CF₃CH₂CF₂H) and1,1,1,2,2,3,3,4,4-nonafluorobutane (CF₃CF₂CF₂CF₂H).

The composition of the invention comprises (A)1,1,2,2,3-pentafluoropropane (R-245ca) which has a boiling point ofabout 25° C. and (B) at least one hydrofluorocarbon selected from1,1,1,3,3-pentafluoropropane (R-245fa) and1,1,1,2,2,3,3,4,4-nonafluorobutane (R-329ccb), both of which have aboiling point of about 15° C. Although component (B) may comprise amixture of R-245fa and R-329ccb, it will preferably comprise just one ofthese compounds and more preferably will comprise just R-329ccb.

The composition of the invention tends to boil and condense over afairly narrow temperature range and, as a result, tends to exhibitfairly small temperature glides in both the evaporator and condenser.Furthermore, the composition tends not to fractionate (separate) intoits constituent components to any significant degree on boiling so thatthe liquid and vapour phases that will be present in the refrigerationcycle will tend to have similar compositions. The terms azeotrope andazeotropic are well known of course and refer to compositions comprisingtwo or more components which exhibit constant boiling behaviour andwhich do not fractionate into their constituent components upon boilingor evaporation. Thus, the composition of the invention exhibitsproperties which are not too far removed from that of a true azeotropeand in this regard may be termed azeotrope-like or near-azeotropic.

The amounts of the R-245ca and of the at least one hydrofluorocarbonselected from R-245fa and R-329ccb in the composition of the inventionmay be varied within wide limits, but typically the composition willcomprise from 10 to 90% by weight of R-245ca and from 10 to 90% byweight of at least one hydrofluorocarbon selected from R-245fa andR-329ccb.

When component (B) is R-245fa, a preferred composition of the inventionin terms of its suitability as a replacement for refrigerant R-11 is onecomprising from 15 to 85% by weight of R-245ca and from 15 to 85% byweight of R-245fa.

When component (B) is R-245fa, a particularly preferred composition ofthe invention in terms of its suitability as a replacement forrefrigerant R-11 is one comprising from 20 to 30% by weight, moreparticularly about 25% by weight, of R-245ca and from 70 to 80% byweight, more particularly about 75% by weight, of R-245fa.

When component (B) is R-245fa, another particularly preferredcomposition of the invention in terms of its suitability as areplacement for refrigerant R-11 is one comprising from 45 to 55% byweight, more particularly about 50% by weight, of R-245ca and from 45 to55% by weight, more particularly about 50% by weight, of R-245fa.

When component (B) is R-245fa, a further particularly preferredcomposition of the invention in terms of its suitability as areplacement for refrigerant R-11 is one comprising from 70 to 80% byweight, more particularly about 75% by weight, of R-245ca and from 20 to30% by weight, more particularly about 25% by weight, of R-245fa.

When component (B) is R-329ccb, a preferred composition of the inventionin terms of its suitability as a replacement for refrigerant R-11 is onecomprising from 40 to 95% by weight of R-245ca and from 5 to 60% byweight of R-329ccb.

When component (B) is R-329ccb, a particularly preferred composition ofthe invention in terms of its suitability as a replacement forrefrigerant R-11 is one comprising from 40 to 80% by weight, moreparticularly from 70 to 80% by weight, of R-245ca and from 20 to 60% byweight, more particularly from 20 to 30% by weight, of R-329ccb. Anespecially preferred composition of the invention in terms of itssuitability as a replacement for refrigerant R-11 is one comprisingabout 75% by weight of R-245ca and about 25% by weight of R-329ccb.

The refrigerant composition of the invention may also be combined withone or more hydrocarbons in an amount which is sufficient to allow thecomposition to transport a mineral oil or alkyl benzene type lubricantaround a refrigeration circuit and return it to the compressor. In thisway, inexpensive lubricants based on mineral oils or alkyl benzenes maybe used to lubricate the compressor.

Suitable hydrocarbons for inclusion in the refrigerant composition ofthe invention are those containing from 2 to 6 carbon atoms, withhydrocarbons containing from 3 to 5 carbon atoms being preferred.Hydrocarbons that will not significantly alter the refrigerantthermophysical properties at the level at which they provide for oiltransport, such as the linear and branched isomers of butane and pentaneare particularly preferred, with pentane being especially preferred.

Where a hydrocarbon is included, it will preferably be present in anamount of from 1 to 10% by weight on the total weight of the refrigerantcomposition.

The refrigerant composition of the invention may also be used incombination with the types of lubricants which have been speciallydeveloped for use with hydrofluorocarbon based refrigerants. Suchlubricants include those comprising a polyoxyalkylene glycol base oil.Suitable polyoxyalkylene glycols include hydroxyl group initiatedpolyoxyalkylene glycols, e.g. ethylene and/or propylene oxideoligomers/polymers initiated on mono- or polyhydric alcohols such asmethanol, butanol, pentaerythritol and glycerol. Such polyoxyalkyleneglycols may also be end-capped with suitable terminal groups such asalkyl, e.g. methyl groups. Another class of lubricants which have beendeveloped for use with hydrofluorocarbon based refrigerants and whichmay be used in combination with the present refrigerant compositions arethose comprising a neopentyl polyol ester base oil derived from thereaction of at least one neopentyl polyol and at least one aliphaticcarboxylic acid or an esterifiable derivative thereof. Suitableneopentyl polyols for the formation of the ester base oil includepentaerythritol, polypentaerythritols such as di- andtripentaerythritol, trimethylol alkanes such as trimethylol ethane andtrimethylol propane, and neopentyl glycol. The esters may be formed withlinear and/or branched aliphatic carboxylic acids, such as linear and/orbranched alkanoic acids. Preferred acids are selected from the C₅₋₈,particularly the C₅₋₇, linear alkanoic acids and the C₅₋₁₀, particularlythe C₅₋₉, branched alkanoic acids. A minor proportion of an aliphaticpolycarboxylic acid, e.g. an aliphatic dicarboxylic acid, may also beused in the synthesis of the ester in order to increase the viscositythereof. Usually, the amount of the carboxylic acid(s) which is used inthe synthesis will be sufficient to esterify all of the hydroxyl groupscontained in the polyol, although residual hydroxyl functionality may beacceptable.

The composition of the present invention may be used to provide thedesired cooling in heat transfer devices such as chillers by a methodwhich involves condensing the composition and thereafter evaporating itin a heat exchange relationship with a heat transfer fluid to be cooled.In particular, the composition of the invention may be employed as areplacement for refrigerant R-11 in chillers.

In addition to its use as a refrigerant, the composition of theinvention may also be used as an aerosol propellant, as a foam blowingagent for blowing polyolefin, polyurethane and related foams, or as asolvent in degreasing or extraction applications.

The present invention is now illustrated but not limited with referenceto the following examples.

EXAMPLE 1

The performance of three refrigerant compositions of the invention in arefrigeration cycle was evaluated using standard refrigeration cycleanalysis techniques in order to assess the suitability thereof as areplacement for R-11. The operating conditions which were used for theanalysis were chosen as being typical of those conditions which arefound in a chiller or air conditioning system, and counter current flowat the heat exchangers was assumed.

The evaluation involved first defining the inlet and outlet temperaturesof the heat transfer fluid, which could be air or water for example, ateach heat exchanger (evaporator and condenser). The temperatures in theevaporator and condenser, assuming that a pure (single component)refrigerant was used in the cycle, were then chosen and thesetemperatures together with the inlet and outlet temperatures of the heattransfer fluid referred to above were used to determine a target logmean temperature difference for each heat exchanger. In the cycleanalysis itself, the refrigerant inlet and outlet temperatures at boththe evaporator and condenser were adjusted until the target log meantemperature difference was achieved for each heat exchanger. When thetarget log mean temperature difference for each heat exchanger wasachieved, the various properties of the refrigerant composition in thecycle were recorded.

The following refrigerant compositions were subjected to the cycleanalysis:

(1) A composition comprising 75% by weight R-245ca and 25% by weightR-245fa.

(2) A composition comprising 50% by weight R-245ca and 50% by weightR-245fa.

(3) A composition comprising 25% by weight R-245ca and 75% by weightR-245fa.

The following operating conditions were used in the cycle analysis.

EVAPORATOR: Evaporator Temperature:  5° C. Inlet Temperature of HeatTransfer Fluid 20° C. Outlet Temperature of Heat Transfer Fluid 12° C.Log Mean Temperature Difference for Evaporator 10.5° C. CONDENSER:Condenser Temperature: 32° C. Inlet Temperature of Heat Transfer Fluid20° C. Outlet Temperature of Heat Transfer Fluid 30° C. Log MeanTemperature Difference for Condenser  5.58° C. Amount of Superheat:  5°C. Amount of Subcooling:  5° C. Isentropic Compressor Efficiency: 75%Volumetric Flow through Compressor  1 m³/s

The results of analysing the performance of the three refrigerantcompositions in a refrigeration cycle using these operating conditionsare given in Table 1.

The performance parameters of the refrigerant compositions which arepresented in Table 1 and in Table 2, i.e. condenser pressure, evaporatorpressure, discharge temperature, refrigeration capacity (by which ismeant the cooling duty achieved per unit swept volume of thecompressor), coefficient of performance (COP) (by which is meant theratio of cooling duty achieved to mechanical energy supplied to thecompressor), and the glides in the evaporator and condenser (thetemperature range over which the refrigerant composition boils in theevaporator and condenses in the condenser), are all art recognisedparameters.

The performance of refrigerant R-11 under the same operating conditionsis also shown in Table 1 by way of comparison.

It is apparent from Table 1 that refrigerant compositions of theinvention containing R-245ca and R-245fa have small temperature glidesin both the evaporator and condenser, i.e. they display azeotrope-likeor near azeotropic behaviour. It is also apparent from Table 1 that theR-245ca/R-245fa compositions tested had a higher refrigeration capacitythan R-11 while maintaining a very similar coefficient of performance.In addition to this, the discharge temperatures of the R-245ca/R-245facompositions tested were appreciably less than that of refrigerant R-11,and although the evaporator and condenser pressures of the compositionswere generally higher than for R-11, they were comparable.

It is further evident from the results given in Table 1 that theperformance of refrigerant compositions of the invention containingR-245ca and R-245fa is such that they could make an acceptablereplacement for refrigerant R-11.

EXAMPLE 2

The performance of three refrigerant compositions of the invention in arefrigeration cycle was evaluated using exactly the same technique andexactly the same operating conditions as described in Example 1.

The following refrigerant compositions were subjected to the cycleanalysis:

(1) A composition comprising 75% by weight R-245ca and 25% by weightR-329ccb.

(2) A composition comprising 50% by weight R-245ca and 50% by weightR-329ccb.

(3) A composition comprising 25% by weight R-245ca and 75% by weightR-329ccb.

The results of analysing the performance of these three refrigerantcompositions in a refrigeration cycle are given in Table 2.

The performance of refrigerant R-11 under the same operating conditionsis also shown in Table 2 by way of comparison.

It is apparent from Table 2 that refrigerant compositions of theinvention containing R-245ca and R-329ccb have small temperature glidesin both the evaporator and condenser, i.e. they display azeotrope-likeor near azeotropic behaviour. It is also apparent from Table 2 that theR-245ca/R-329ccb compositions tested had a higher refrigeration capacitythan R-11 while maintaining a similar coefficient of performance. Inaddition to this, the discharge temperatures of the R-245ca/R-329ccbcompositions tested were appreciably less than that of refrigerant R-11,and although the evaporator and condenser pressures of the compositionswere generally higher than for R-11, they were comparable.

It is further evident from the results given in Table 2 that theperformance of refrigerant compositions of the invention containingR-245ca and R-329ccb is such that they could make an acceptablereplacement for refrigerant R-11.

TABLE 1 R-245ca/ R-245ca/ R-245ca/ Refrigerant R-11 R-245fa R-245faR-245fa % by weight 100 75/25 50/50 25/75 Evaporator Pressure 0.5 0.490.54 0.59 (bar) Condenser Pressure 1.34 1.46 1.59 1.73 (bar) Discharge52.79 41.83 41.46 40.99 Temperature (° C.) Coefficient of 7.21 7.21 7.27.15 Performance (COP) COP Relative to R-11 1 1 1 0.99 RefrigerationCapacity 495.05 529.1 574.71 621.12 (KW/m³) Refrigeration Capacity 11.07 1.16 1.25 Relative to R-11 Evaporator Glide 0 0.54 0.74 0.57 (° C.)Condenser Glide 0 0.57 0.77 0.59 (° C.)

TABLE 2 R-245ca/ R-245ca/ R-245ca/ Refrigerant R-11 R-329ccb R-329ccbR-329ccb % by weight 100 75/25 50/50 25/75 Evaporator Pressure 0.5 0.470.52 0.58 (bar) Condenser Pressure 1.34 1.42 1.51 1.65 (bar) Discharge52.79 39.37 36.49 33.39 Temperature (° C.) Coefficient of 7.21 7.15 7.16.96 Performance (COP) COP Relative to R-11 1 0.99 0.98 0.97Refrigeration Capacity 495.05 507.61 537.63 571.43 (KW/m³) RefrigerationCapacity 1 1.03 1.09 1.15 Relative to R-11 Evaporator Glide 0 0.46 0.780.78 (° C.) Condenser Glide 0 0.38 0.65 0.65 (° C.)

What is claimed is:
 1. A composition comprising: (A)1,1,2,2,3-pentafluoropropane (R-245ca); and (B)1,1,1,3,3-pentafluoropropane (R-245fa).
 2. A composition as claimed inclaim 1 comprising: (A) from 10 to 90% by weight of R-245ca; and (B)from 10 to 90% by weight of R-245fa.
 3. In a method of cooling whichcomprises condensing refrigerant R-11, the improvement which comprisesreplacing the R-11 with the composition of claim
 1. 4. A composition asclaimed in claim 1 comprising from 15 to 85% by weight of R-245ca andfrom 15 to 85% by weight of R-245fa.
 5. A composition as claimed inclaim 4 comprising from 20 to 30% by weight of R-245ca and from 70 to80% by weight of R-245fa.
 6. A composition as claimed in claim 5comprising about 25% by weight of R-245ca and about 75% by weight ofR-245fa.
 7. A composition as claimed in claim 4 comprising from 45 to55% by weight of R-245ca and from 45 to 55% by weight of R-245fa.
 8. Acomposition as claimed in claim 7 comprising about 50% by weight ofR-245ca and about 50% by weight, of R-245fa.
 9. A composition as claimedin claim 4 comprising from 70 to 80% by weight of R-245ca and from 20 to30% by weight of R-245fa.
 10. A composition as claimed in claim 1 whichadditionally comprises at least one hydrocarbon.
 11. A composition asclaimed in claim 10, wherein the least one hydrocarbon comprisespentane.
 12. A composition as claimed in claim 10 or claim 11 whereinthe hydrocarbon is present in an amount of from 1 to 10% by weight onthe total weight of the composition.
 13. A heat transfer devicecontaining a composition as claimed in claim
 1. 14. A method forproviding cooling which comprises condensing a composition as claimed inclaim 1 and thereafter evaporating it in a heat exchange relationshipwith a heat transfer fluid to be cooled.
 15. A composition as claimed inclaim 9 comprising about 75% by weight of R-245ca and about 25% byweight of R-245fa.